Method for curing aminoplast resins

ABSTRACT

The invention relates to a method for curing aminoplast resins according to which inorganic particles, which have a laminated structure and which comprise interlamellarly exchangeable cations of the flowing type: alkali cations, alkaline-earth cations, aluminium cations, iron cations and/or manganese cations, are used as curing agents. The invention also relates to aminoplast resins cured in such a manner, to semi-finished products and to molding materials.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Phase Patent Application of InternationalApplication Number PCT/EP01/14582, filed on Dec. 12, 2001, which claimspriority of Austrian Patent Application Number A 2088/2000, filed Dec.15, 2000.

The invention relates to a process for curing aminoplast resins havingimproved toughness, and aminoplast resins cured in this manner.

Semifinished products and moldings of aminoplasts, such as compressionmoldings, injection moldings, profiles, fibers, foams, coatings andlaminates, are known (Ullmann's Encyclopedia of Industrial Chemistry,4th edition, Vol. A2, 115-141). A disadvantage of the semifinishedproducts and moldings of aminoplasts is their poor toughness.

A number of processes for improving the toughness of semifinishedproducts and moldings of aminoplasts are known.

Moldings of melamine resins having a high toughness are obtained bymeans of melamine resin formulations in which some of the melaminecomponent is replaced by melamine substituted by hydroxyoxyalkyl groups(EP 0 408 947), or by means of incorporation of glycols into themelamine resin (EP 0 149 652). In the preparation of melamine resinfoams, an improvement in the toughness is achieved if foaming andcrosslinking are effected by exposure to microwave radiation (EP 0 037470). The brittleness of melamine resin laminates is reduced by usingmelamine resins which contain dicyandiamide and polyalcoholsincorporated into the melamine resin component (WO 96 20 230).

In the preparation of foams based on urea resins, foams having improvedtoughness are obtained if urea resins modified with polyalcohols, suchas pentaerythritol, arabitol or sorbitol (DAS 1 054 232) or withpolyethylene glycols (U.S. Pat. No. 2,807,595) are used.

A disadvantage of these processes is that the increase in the toughnessis associated with a decrease in the strength of the semifinishedproducts and moldings.

The toughness of semifinished products and moldings of aminoplasts isfurthermore determined by the curing agents used and the degree ofcuring. Known curing agents for aminoplasts are p-toluenesulfonic acid,naphthalenesulfonic acid, phthalic acid, maleic acid and amine andammonium salts of inorganic acids (Woebcken, W., Kunststoff-Handbuch[Plastics Handbook], Vol. 10, 2nd edition, Carl-Hanser-Verlag, Munich1988). The possibilities for improving the toughness of aminoplasts withcontrol of the course of curing by curing temperature and pH range are,however, limited.

It has surprisingly been found that aminoplasts having high toughnessand strength can be prepared by using curing agents comprising inorganicparticles having a layer structure which have an interlamellar contentof exchangeable cations.

The invention accordingly relates to a process for curing aminoplastresins, which is characterized in that inorganic particles having alayer structure which have an interlamellar content of exchangeablecations of the type consisting of alkali metal, alkaline earth metal,aluminum, iron and/or manganese cations are used as the curing agent.

In one embodiment, the aminoplast resins and the semifinished productsand moldings produced therefrom contain, as curing agents, from 1 to 30%by mass, based on the semifinished products and moldings, of inorganicparticles having a layer structure which have an interlamellar contentof exchangeable cations of the type consisting of alkali metal, alkalineearth metal, aluminum, iron and/or manganese cations, it being possiblefor the semifinished products and moldings optionally to contain, basedin each case on the aminoplast resins, from 20 to 5 000% by mass ofsheet-like substrate materials, from 1 to 400% by mass of fillers and/orreinforcing materials, from 0.1 to 5% by mass of polymeric dispersantsand/or from 0.1 to 5% by mass of customary additives.

The semifinished products and moldings are preferably compressionmoldings, injection moldings, profiles, microcapsules, fibers,closed-cell or open-cell foams, coatings, laminates or impregnatedsheet-like substrate materials.

Preferred aminoplast resins are melamine resins, urea resins, cyanamideresins, dicyandiamide resins, guanamine resins, sulfonamide resinsand/or aniline resins.

Preferred melamine resins are polycondensates of melamine or melaminederivatives and C₁-C₁₀-aldehydes having a molar melamine or melaminederivative/C₁-C₁₀-aldehydes ratio of from 1:1 to 1:6 and the partialetherification products thereof with C₁-C₁₀-alcohols, the melaminederivatives being in particular melamines, diaminomethyltriazines and/ordiaminophenyltriazines substituted by hydroxy-C₁-C₁₀-alkyl groups,hydroxy-C₁-C₄-alkyl(oxa-C₂-C₄-alkyl)₁₋₅ groups and/or byamino-C₁-C₁₂-alkyl groups, particularly preferably2-(2-hydroxyethylamino)-4,6-diamino-1,3,5-triazine,2-(5-hydroxy-3-oxapentylamino)-4,6-diamino-1,3,5-triazine and/or2,4,6-tris(6-aminohexylamino)-1,3,5-triazine ammeline, ammelide, melem,melon, melam, benzoguanamine, acetoguanamine,tetramethoxymethyl-benzoguanamine, caprinoguanamine and/orbutyroguanamine, and the C₁-C₁₀-aldehydes being in particularformaldehyde, acetaldehyde, trimethylolacetaldehyde, acrolein, furfurol,glyoxal and/or glutaraldehyde, particularly preferably formaldehyde.

The melamine resins may likewise contain from 0.1 to 10% by mass, basedon the total mass of the melamine and melamine derivatives, ofincorporated phenols and/or urea. Suitable phenol components includephenol, C₁-C₉-alkylphenols, hydroxyphenols and/or bisphenols.

Examples of partial etherification products of melamine resins withC₁-C₁₀-alcohols are methylated and butylated melamine resins.

Examples of the urea resins optionally contained as aminoplasts in thesemifinished products or moldings can also be cocondensates withphenols, acid amides or sulfonamides, in addition to urea/formaldehyderesins.

Examples of the sulphonamide resins optionally contained as aminoplastsin the semifinished products or moldings are sulfonamide resins ofp-toluenesulfonamide and formaldehyde.

Examples of guanamine resins optionally contained as aminoplasts in thesemifinished products or moldings are resins which contain, as aguanamine component, benzoguanamine, acetoguanamine,tetramethoxymethylbenzoguanamine, caprinoguanamine and/orbutyroguanamine.

Examples of the aniline resins optionally contained as aminoplasts inthe semifinished products or moldings are aniline resins which, inaddition to aniline, may also contain toluidine and/or xylidenes asaromatic diamines.

The inorganic particles having a layer structure and contained in thesemifinished products and moldings of aminoplasts are preferablysilicates, phosphates, arsenates, titanates, vanadates, niobates,molybdates and/or manganates, particularly preferably sheet silicates ofthe type consisting of montmorillonite, bentonite, kaolinite, muscovite,hectorite, fluorohectorite, kanemite, revdite, grumantite, ilerite,saponite, beidelite, nontronite, stevensite, laponite, taneolite,vermiculite, halloysite, volkonskoite, magadite, rectorite, halloysite,kenyaite, sauconite, borofluorophlogopites and/or synthetic sheetsilicates.

Examples of suitable phosphates having a layer structure are compoundsof the formula H₂[M^(IV)(PO₄)₂].xH₂O (M^(IV)═Zr, Ti, Ge, SN, Pb) andCaPO₄R.H₂O (R═CH₃; C₂H₅).

Examples of suitable arsenates having a layer structure are compounds ofthe formula H₂[M^(IV)(AsO₄)₂].xH₂O and H[Mn(AsO₄)₂].xH₂O.

Examples of suitable titanates having a layer structure are compounds ofthe formula Na₄Ti₉O₂₀.xH₂O and K₂Ln₂Ti₃O_(10x)H₂O.

Synthetic sheet silicates are obtained, for example, by reacting naturalsheet silicates with sodium hexafluorosilicate.

Particularly preferred sheet silicates are those whose layers have aninterlayer spacing of from about 0.4 nm to 1.5 nm.

Preferred sheet-like substrate materials which may be contained in thesemifinished products and moldings according to the invention are paper,board, wood products, wood fiber boards, wood chip boards, woven glassfiber fabrics, nonwovens, woven textile fabrics, plastics films,plastics sheets, sheet-like plastics parts, metal foils and sheet-likemetal parts, such as bodywork parts in the automotive sector or coversin apparatus construction and mechanical engineering.

Fillers which may be contained in the semifinished products or moldingsaccording to the invention are Al₂O₃, Al(OH)₃, barium sulfate, calciumcarbonate, glass beads, silica, mica, quartz powder, slate powder,hollow microspheres, carbon black, talc, crushed rock, woodmeal,cellulose powder and/or shell flours and kernel flours, such as peanutshell flour or olive kernel flour.

Examples of reinforcing materials which may be contained in thesemifinished products or moldings according to the invention are woodfibers, cellulose fibers, flax, jute and kenaf.

Preferred reinforcing materials are inorganic fibers, in particularglass fibers and/or carbon fibers, natural fibers, in particularcellulose fibers, and/or plastics fibers, in particular fibers ofpolyacrylonitrile, polyvinyl alcohol, polyvinyl acetate, polypropylene,polyesters and/or polyamides.

Preferred polymeric dispersants which may be contained in thesemifinished products or moldings according to the invention arewater-soluble, water-dispersible and/or water-emulsifiable polymers.

Examples of water-soluble polymers which may be contained in thesemifinished products or moldings according to the invention arepolyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, polyethyleneoxide, methylcellulose, ethylcellulose, hydroxyethylcellulose and/orcarboxymethylcellulose.

The water-dispersible or water-emulsifiable polymers optionallycontained in the semifinished products and moldings according to theinvention are thermoplastics, elastomers and/or waxes.

Examples of suitable thermoplastics are cellulose esters, celluloseethers, polyvinyl acetate, polyvinyl propionate, polyacrylates,unsaturated or saturated polyesters, maleic anhydride copolymers,polypropylene oxide and/or ethylene/vinyl acetate copolymers. Preferredmaleic anhydride copolymers are copolymers in which the anhydride groupshave been modified by amidation and/or imidation with hydrophobichydrocarbon constituents or by esterification with hydrophilicpolyalkylene oxide substituents.

Examples of water-dispersible or water-emulsifiable elastomers arestyrene/butadiene rubbers, acrylate rubbers, polyurethanes and/orfluoroelastomers.

Examples of suitable waxes are polyolefin wax oxidates, such aspolyethylene wax oxidates, or waxes based on ethylene/vinyl acetatecopolymers.

Particularly preferred polymeric dispersants which are optionallycontained in the semifinished products and moldings according to theinvention are polyvinyl alcohol, polyvinyl acetate, maleic anhydridecopolymers and/or unsaturated or saturated polyesters.

The customary additives which may be contained in the semifinishedproducts and moldings according to the invention are in particular from0.1 to 30% by mass of flameproofing agents and/or from 0.05 to 1% bymass of stabilizers.

Examples of suitable flameproofing agents which may optionally becontained in the semifinished products or moldings are ammoniumphosphate, ammonium polyphosphate, antimony trioxide, magnesiumphosphate, decabromodiphenyl ether, trisdibromopropyl isocyanurate,tetrabromobisphenol-bis-dibromopropyl ether and/ortris(trisbromoneopentyl) phosphate.

Examples of suitable stabilizers which may be used in particular incoatings comprising coating resin arebis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate or benzotriazolederivatives, such as2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole or2-(2-hydroxy-3-tert-butyl-5-methylphenyl)benzotriazole.

The semifinished products and moldings of aminoplasts having improvedtoughness are produced, according to the invention, by a process inwhich, by methods known per se, mixtures of aminoplast precondensatesand, as a curing agent, from 1 to 30% by mass, based on the aminoplastprecondensates, of inorganic particles having a layer structure whichhave an interlamellar content of exchangeable cations of the typeconsisting of alkali metal, alkaline earth metal, aluminum, iron and/ormanganese cations, in the form of aqueous dispersions or emulsionshaving a solids content of from 30 to 80% by mass, which may optionallycontain up to 50% by mass of C₁-C₈-alcohols, from 0.1 to 5% by mass ofpolymeric dispersants and from 0.01 to 3% by mass of detergents,

-   -   are shaped and cured after drying and subsequent thermal        processing of the molding materials by compression molding,        injection molding, melt spinning or extrusion to give        compression moldings, injection moldings, filaments or profiles,        or    -   are processed after concentration of the aqueous solutions by        centrifugal spinning, filament drawing, extrusion or        fibrillation processes, optionally with subsequent orientation,        and curing to give aminoplast fibers, or    -   are processed by introduction into an emulsifier-free aqueous        dispersion of solid or liquid capsule core formers, curing and        spray-drying to give microcapsules, or    -   are processed by introduction into an emulsifier-free aqueous        dispersion of volatile hydrocarbons, inert gases and/or        inorganic carbonates and discharge of the hollow particles        either into molds and curing to give closed-cell foams or by        means of a mold and curing to give closed-cell foamed profiles,        or    -   by introduction into an aqueous blowing agent emulsion of        volatile hydrocarbons, inert gases and/or inorganic carbonates,        heating to the boiling point or decomposition temperature of the        blowing agent and discharge either into molds and curing to give        open-cell foams or by means of a mold and curing to give        open-cell foamed profiles, or    -   are processed after formulation to give coating resin solutions        or coating resin dispersions and by subsequent application of        the coating resin solutions or coating resin dispersions to        sheet-like substrate materials, drying and curing to give        coatings comprising coating resin, or    -   after formulation to give impregnating resin solutions or        impregnating resin dispersions, are subsequently processed by        impregnation of sheet-like substrate materials, lamination and        curing to give laminates,    -   it being possible to add, in each case based on the aminoplasts,        from 1 to 400% by mass of fillers and/or reinforcing materials        and/or from 0.1 to 5% by mass of customary additives before        and/or during the processing to give semifinished products or        moldings.

The customary additives which may be used in the process according tothe invention for the production of semifinished products and moldingsof aminoplasts having improved toughness may be from 0.1 to 3% by mass,preferably from 0.1 to 0.6% by mass, of surfactants, from 0.1 to 2% bymass of lubricants, from 0.1 to 30% by mass of flameproofing agentsand/or from 0.05 to 1% by mass of stabilizers.

Surfactants which may be used in the process for the production ofsemifinished products and moldings are saturated or unsaturatedC₁₂-C₂₂-hydrocarbons having hydroxyl and/or carboxyl groups, anionicsurfactants, cationic surfactants or nonionic surfactants.

Examples of saturated C₁₂-C₂₂-hydrocarbons having hydroxyl and/orcarboxyl groups are lauric acid, stearic acid, behenic acid, laurylalcohol, stearyl alcohol and behenyl alcohol.

Examples of unsaturated C₁₂-C₂₂-hydrocarbons having hydroxyl and/orcarboxyl groups are linoleic acid, linolenic acid, eleostearic acid,oleic acid, erucic acid, oleyl alcohol, elaidyl alcohol and erucylalcohol.

Examples of anionic surfactants are metal salts, such as sodium salts ofalkanesulfonates and alkylarylsulfonates having 8 to 20 C atoms in thealkyl radical, metal salts of sulfosuccinic esters, sulfonated castoroils, alkylnaphthalenesulfonic acids, phenolsulfonic acids and sulfuricesters, such as C₁₂-C₁₈-alkyl hydrogen sulfates or C₁₆-C₁₈ fatty alcoholsulfates.

Examples of cationic surfactants are the triethanolamine ester of oleicacid and laurylpyridinium chloride.

Examples of nonionic surfactants are ethoxylated castor oil, ethoxylatedtalcum fatty alcohols, ethoxylated stearic acid or oleic acid andethoxylated nonylphenol.

The formulation of the molding materials for the production of thecompression moldings, injection moldings or profiles can be effected inparticular by wet impregnation or dry impregnation. In the case of thewet impregnation process, the solution of the aminoplast precondensate,which contains inorganic particles having a layer structure withexchangeable cations of the type consisting of alkali metal, alkalineearth metal, aluminum, iron and/or manganese cations in interlamellarsites as a curing agent in dispersed form, is homogenized in kneaderswith the fillers, such as pulp, woodmeal, textile shreds, textilefibers, paper shreds, paper fibers or glass fibers, and customaryadditives, such as lubricants and pigments, and dried in drying drums attemperatures of below 80° C. In the case of the dry impregnationprocess, comminuted solid aminoplast resins or spray-dried solidaminoplast resins, which contains inorganic particles having a layerstructure with exchangeable cations of the type consisting of alkalimetal, alkaline earth metal, aluminum, iron and/or manganese cations ininterlamellar sites as a curing agent, are premixed in dry form withfillers, such as woodmeal or crushed rock, and customary additives, suchas lubricants and pigments, and homogenized on roll mills or continuouskneaders. Preferred processing temperatures are from 140° C. to 170° C.in the case of the production of compression moldings and from 155° C.to 180° C. in the case of the production of injection moldings

Suitable processing assistants which can be added as customary additivesin the production of semifinished products or moldings are calciumstearate, magnesium stearate and/or waxes.

In the production of melamine resin fibers as aminoplast semifinishedproducts, melamine is condensed with formaldehyde and/or mixtures offrom 20 to 99.9% by mass of melamine and from 0.1 to 80% by mass ofmelamine derivatives and/or triazine derivatives, optionally withaddition of from 0.1 to 10% by mass, based on the total mass of themelamine, melamine derivatives and/or triazine derivatives, of phenols,are condensed with formaldehyde, the molar melamine/formaldehyde ormelamine+melamine derivative or triazine derivative/formaldehyde ratiopreferably being from 1:1.0 to 1:4. The fiber production is carried outfrom the highly concentrated aqueous solutions of the polycondensates(solids content from 50 to 70% by mass) after addition of the inorganicparticles having a layer structure, which have an interlamellar contentof exchangeable cations of the type consisting of alkali metal, alkalineearth metal, aluminum, iron and/or manganese cations, as a curing agent,by centrifugal spinning, filament drawing, extrusion or fibrillationprocesses, optionally subsequent orientation, and curing. In theextrusion process, the spinning solution is forced through a nozzle intoan atmosphere (air or inert gas) heated to 170 to 320° C., in order toremove the solvents contained in the spinning solution and to cure thefibers in as short a time as possible.

The production of microcapsules is effected by introduction of theaminoplast precondensates into an emulsifier-free aqueous dispersion ofsolid or liquid capsule core formers and inorganic particles having alayer structure, which have an interlamellar content of exchangeablecations of the type consisting of alkali metal, alkaline earth metal,aluminum, iron and/or manganese cations, as a curing agent, andsubsequent curing and spray-drying. The use of the capsule core formersin the production of the microcapsules is determined by the field of useof the microcapsules. Examples of solid capsule core formers are finelydispersed photographic chemicals, herbicides, pesticides, agrochemicals,pharmaceuticals, pigments, dyes, flameproofing agents, catalysts,magnetic particles and stabilizers. Examples of liquid capsule coreformers are adhesives, flavors, perfumes, inks and water-dispersibleliquids, such as oils.

In the preparation of the closed-cell foams or closed-cell foamedprofiles as aminoplast semifinished products, it is advantageous, forobtaining a finely divided emulsifier-free aqueous dispersion of thevolatile hydrocarbons and/or inert gases used, to use multiphase gasintroduction pumps. From 1 to 20% by mass, based on the aminoplastprecondensates used, of prepolymers based on epoxy resins, phenolresins, urea resins, melamine resins, aniline resins, resorcinol resinsand/or polyester resins can be added to the hollow particles produced,before processing to give foams or profiles.

Examples of suitable volatile hydrocarbons which can be used in theproduction of the closed-cell or open-cell semifinished products ormoldings of aminoplasts are butane, pentane, isopentane and/or hexane.

In the production of coatings comprising coating resin as aminoplastsemifinished products, aminoplast precondensates are formulated withaddition of inorganic particles having a layer structure withexchangeable cations of the type consisting of alkali metal, alkalineearth metal, aluminum, iron and/or manganese cations in interlamellarsites, as a curing agent, pigments, and optionally fillers, stabilizers,solvents and film formers of the type consisting of alkyd resins, epoxyresins and/or phenol resins, applied to substrate materials, such aswood, and cured at temperatures below 80° C. or applied to metallicsubstrate materials and cured at temperatures up to 180° C.

In the production of laminates as aminoplast semifinished products,according to the invention sheet-like substrate materials comprisingorganic or inorganic fibers in the form of webs, woven fabrics, mats ornonwovens, are impregnated with the aqueous solution of the aminoplastprecondensate, which contain, as a curing agent, inorganic particleshaving a layer structure with an interlamellar content of exchangeablecations of the type consisting of alkali metal, alkaline earth metal,aluminum, iron and/or manganese cations, for example in impregnatingunits, and dried in drying tunnels at temperatures up to 140° C. andcured as a laminate or pressed in multiple-daylight presses aftercutting and optionally introducing intermediate layers, for example madeof wood, paper or board. Improved toughness of laminates is importantfor the subsequent thermal processibility of the laminates, during whichcracking must be ruled out in the case of small bending radii during thesubsequent thermal processing.

The water-soluble, water-dispersible and/or water-emulsifiable polymersoptionally used as polymeric dispersants can, depending on thedispersant, be employed in the form of a solution, dispersion oremulsion in water or organic solvents in the production of thesemifinished products and moldings according to the invention andcomprising aminoplasts.

The water-soluble, water-dispersible and/or water-emulsifiable polymerscan also be formed in situ by adding, to those mixtures of aminoplastprecondensates and inorganic particles having a layer structure whichare present as aqueous dispersions or emulsions, before the processingto semifinished products or moldings, instead of polymeric dispersants,mixtures of ethylenically unsaturated monomers and thermal free radicalinitiators, from which the water-soluble, water-dispersible and/orwater-emulsifiable polymers are formed. Examples of suitableethylenically unsaturated monomers are acrylamide, vinylpyrrolidone,C₄-C₁₈-(meth)acrylic esters and/or vinyl acetate.

The semifinished products and moldings according to the invention,having improved toughness, are suitable, particularly in the form ofcompression moldings, injection moldings or profiles, in the electricalindustry, electronics, in the kitchen and sanitary sector, in theequipment industry and in mechanical engineering; in the form ofmicrocapsules containing solids or liquids, for photosensitive andpressure-sensitive photographic and copying paper and in pharmacy andagrochemistry; in the form of fibers, for filter materials andnonflammable textiles; in the form of closed-cell or open-cell foams,for heat and sound insulation in construction and in the vehicleindustry; in the form of coatings, as baking finishes in the vehicle andequipment industry and for scratch-resistant wood coatings; in the formof impregnated sheet-like substrate materials, in the textile industryand paper industry; and in the form of laminates, in construction and inthe furniture industry.

EXAMPLE 1

35 kg of 30% aqueous formalin solution, 9 kg of melamine, 3 kg ofbenzoguanamine and 2.5 kg of urea are introduced into a 150 literstirred reactor, adjusted to pH=8.0 with sodium hydroxide solution andcondensed at 75° C. with stirring in the course of 40 min. After coolingto room temperature, 900 g of sodium montmorillonite (Südchemie AG,Moosburg, Federal Republic of Germany) are dispersed in the solution ofthe aminoplast precondensate.

In a heatable kneader, a mixture of 3.3 kg of bleached sulfitecellulose, 1 kg of chalk and 120 g of magnesium stearate is impregnatedwith 9 l of the aminoplast solution containing sodium montmorillonite asa curing agent, homogenized, dried at 80° C., discharged and granulated,and the molding material particles are processed in a heatable press ata mold temperature of 170° C. and a pressure of 250 bar to give 4 mmsheets measuring 100×100 mm.

Cut-out Test Bars have the Following Properties:

Tensile strength: 29 MPa Flexural strength: 82 MPa

Flexural modulus of elasticity: 7 600 MPa

Impact strength: 11.0 kJ/m² Notched impact strength: 4.0 kJ/m²

EXAMPLE 2

33 kg of 30% aqueous formalin solution and 10 kg of melamine and 2.2 kgof urea are introduced into a 150 l stirred reactor and condensed at 80°C. with stirring in the course of 120 min. After cooling to roomtemperature, 950 g of aluminum montmorillonite (prepared from sodiummontmorillonite by cation exchange of sodium for aluminum) are added tothe solution of the aminoplast condensate and dispersed.

In a heatable kneader, a mixture of 3.5 kg of textile shreds, 1 kg oflithopone and 120 g of calcium stearate is impregnated with 9.5 l of theaminoplast solution containing aluminum montmorillonite as a curingagent, homogenized, dried at 80° C., discharged and granulated, and themolding material particles are processed in a heatable press at a moldtemperature of 170° C. and a pressure of 250 bar to give 4 mm sheetsmeasuring 100×100 mm.

Cut-out Test Bars have the Following Properties:

Tensile strength: 31 MPa Flexural strength: 85 MPa

Flexural modulus of elasticity: 8 200 MPa

Impact strength: 12.0 kJ/m² Notched impact strength: 5.0 kJ/m²

EXAMPLE 3

30 kg of a 30% aqueous aldehyde solution comprising 9:1formaldehyde/glyoxal, 7.5 kg of melamine, 2 kg of aniline and 2.0 kg of2-(2-hydroxyethylamino)-4,6-diamino-1,3,5-triazine are introduced into a150 l stirred reactor having a reflux condenser and high-speeddisperser, adjusted to pH=7.0 with sodium hydroxide solution andcondensed at 85° C. with stirring in the course of 30 min. After coolingto room temperature, 850 g of sodium montmorillonite (Südchemie AG,Moosburg, Federal Republic of Germany) were introduced into the solutionof the aminoplast precondensate and dispersed.

For the production of the laminates, a decor paper (base weight 80 g/m²)and a kraft paper as a core paper (basis weight 180 g/m²) areimpregnated at 25° C. with the solution of the aminoplast precondensate,which contains sodium montmorillonite (Südchemie AG, Moosburg, FederalRepublic of Germany) as a curing agent and to which in each case 1% bymass of wetting agent and parting agent are also added.

After drying in a through-circulation oven at 140° C. to an alignment of7.2%, the decor paper has a resin content of 55% by mass and the kraftpaper a resin content of 42% by mass. Thereafter, 2 layers of theimpregnated decor paper are compressed with a core paper in between in aCollin laboratory press with a pressure of 100 bar at 160° C. for 130 s.

For testing the toughness, the subsequent deformability of the resultinglaminate was investigated. On bending the laminate around a 3 mm metalspindle heated to 160° C., no cracking of the laminate occurred.

1. A method for curing comprising incorporating an aminoplast resin intoaminoplast condensate inorganic particles having a layer structure whichhave an interlamellar content of exchangeable cations selected from thegroup consisting of alkali metal, alkaline earth metal, aluminum, ironand/or manganese cations to form a mixture; and curing the mixture. 2.The method for curing an aminoplast resin as claimed in claim 1, whereinthe inorganic particles having a layer structure are silicates,phosphates, arsenates, titanates, vanadates, niobates, molybdates and/ormanganates.
 3. The method for curing an aminoplast resin as claimed inclaim 1, wherein the aminoplast resin is selected from melamine resins,urea resins, cyanamide resins, dicyandiamide resins, guanamine resins,sulfonamide resins and/or aniline resins.
 4. The method for curing anaminoplast resin as claimed in claim 1, wherein the aminoplast resin isselected from polycondensates of melamine or melamine derivatives andC₁-C₁₀-aldehydes having a molar melamine or melaminederivative/C₁-C₁₀-aldehydes ratio of from 1:1 to 1:6 and the partialetherification products thereof with C₁-C₁₀-alcohols.
 5. A process forthe preparation of aminoplast resins, having improved toughness, whereininorganic particles having a layer structure, which have aninterlamellar content of exchangeable cations selected from the groupconsisting of alkali metal, alkaline earth metal, aluminum, iron and/ormanganese cations, in the form of aqueous dispersions or emulsionshaving a solids content of 30-80% by mass, which may optionally containup to 50% by mass of C₁-C₈-alcohols, 0.1-5% by mass of polymericdispersants and from 0.01 to 3% by mass of detergents, are added to amixture of aminoplast precondensate and are shaped and cured afterdrying and subsequent thermal processing of the molding materials bycompression molding, injection molding, melt spinning or extrusion togive compression moldings, injection moldings, filaments or profiles, orare processed after concentration of the aqueous solutions bycentrifugal spinning, filament drawing, extrusion or fibrillationprocesses, optionally with subsequent orientation, and curing to giveaminoplast fibers, or are processed by introduction into anemulsifier-free aqueous dispersion of solid or liquid capsule coreformers, curing and spray-drying to give microcapsules, or are processedby introduction into an emulsifier-free aqueous dispersion of volatilehydrocarbons, insert gases and/or inorganic carbonates and discharge ofthe hollow particles either into molds and curing to give closed-cellfoams or by means of a mold and curing to give closed-cell foamedprofiles, or are introduced into an aqueous blowing agent emulsion ofvolatile hydrocarbons, inert gases and/or inorganic carbonates, heatedto the boiling point or decomposition temperature of the blowing agentand discharged either into molds and cured to give open-cell foams or bymeans of a mold and curing to give open-cell foamed profiles, or areprocessed after formulation to give coating resin solutions or coatingresin dispersions and by subsequent application of the coating resinsolutions or coating resin dispersions to sheet-like substratematerials, drying and curing to give coatings comprising coating resin,or after formulation to give impregnating resin solutions orimpregnating resin dispersions, are subsequently processed byimpregnation of sheet-like substrate materials, lamination and curing togive laminates, and optionally adding, in each case based on theaminoplasts, from 1 to 400% by mass of fillers and/or reinforcingmaterials and/or from 0.1 to 5% by mass of customary additives are addedbefore and/or during the processing.
 6. An aminoplast resin cured withthe aid of inorganic particles having a layer structure, which have aninterlamellar content of exchangeable cations of the type consisting ofalkali metal, alkaline earth metal, aluminum, iron and/or manganesecations.
 7. The cured aminoplast resin as claimed in claim 6, wherein itis in the form of a compression molding, injection molding, profile,microcapsule, fiber, closed-cell or open-cell foam, coating, laminate orimpregnated sheet-like substrate material.
 8. (Canceled)
 9. The methodfor curing an aminoplast resin as claimed in claim 1, wherein theinorganic particles having a layer structure are sheet silicatesselected from the group consisting of montmorillonite, bentonite,kaolinite, muscovite, hectorite, fluorohectorite, kanemite, revdite,grumantite, ilerite, saponite, beidelite, nontronite, stevensite,laponite, taneolite, vermiculite, volkonskoite, magadite, rectorite,halloysite, kenyaite, sauconite, borofluorophlogopites and/or syntheticsheet silicates.
 10. The method for curing an aminoplast resin asclaimed in claim 4, wherein the melamine derivatives is selected frommelamines, diaminomethyltriazines and/or diaminophenyltriazinessubstituted by hydroxy-C₁-C₁₀-alkyl groups,hydroxy-C₁-C₄-alkyl(oxa-C₂-C₄-alkyl)₁₋₅ groups and/or byamino-C₁-C₁₂-alkyl groups, ammeline, ammelide, melem, melon, melam,benzoguanamine, acetoguanamine, tetramethoxymethylbenzoguanamine,caprinoguanamine and/or butyroguanamine, and the C₁-C₁₀-aldehydespreferably being formaldehyde, acetaldehyde, trimethyolacetaldehyde,acrolein, furfurlol, glyoxal and/or glutaraldehyde.
 11. The method forcuring an aminoplast resin as claimed in claim 10, wherein the melaminederivative is 2-(2-hydroxyethylamino)-4,6-diamino-1,3,5-triazine,2-(5-hydroxy-3-oxapentylamino)-4,6-diamino-1,3,5-triazine and/or2,4,6-tris(6-aminohexylamino)-1,3,5-triazine.
 12. The method for curingan aminoplast resin as claimed in claim 10, wherein the C₁-C₁₀-aldehydeis selcted from formaldehyde, acetaldehyde, trimethyolacetaldehyde,acrolein, furfurlol, glyoxal and/or glutaraldehyde.